<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			div{
				width: 100px;
				height: 100px;
				background-color: red;
				margin-bottom: 50px;
			}
			.p1{
				resize: both;
				overflow: auto;
			}
			.p2{
				border: 10px solid blue;
			}
			.p3{
				box-sizing: border-box;
				border: 10px solid blue;
			}
			.p4{
				box-sizing: border-box;
				border: 5px solid black;
				outline: 2px solid red;
				outline-offset: 15px;
			}
		</style>
	</head>
	<body>
		<div class="p1"></div>
		<!--box-sizing: content-box -->
		<div class="p2"></div>
		<!--box-sizing: border-box-->
		<div class="p3"></div>
		<!--CSS3 外形修饰（outline-offset ）-->
		<div class="p4"></div>
	</body>
</html>